Research Article 2823 SUMOylation modulates the function of Aurora-B kinase Gonzalo Fernández-Miranda1, Ignacio Pérez de Castro1, Mar Carmena2, Cristina Aguirre-Portolés1, Sandrine Ruchaud2, Xavier Fant2, Guillermo Montoya3, William C. Earnshaw2 and Marcos Malumbres1,* 1Cell Division and Cancer Group, Spanish National Cancer Research Center (CNIO), Madrid, E-28029, Spain 2Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, EH9 3JR, UK 3Macromolecular Crystallography Group, CNIO, Madrid, Spain *Author for correspondence ([email protected]) Accepted 13 May 2010 Journal of Cell Science 123, 2823-2833 © 2010. Published by The Company of Biologists Ltd doi:10.1242/jcs.065565 Summary Aurora kinases are central regulators of mitotic-spindle assembly, chromosome segregation and cytokinesis. Aurora B is a member of the chromosomal passenger complex (CPC) with crucial functions in regulation of the attachment of kinetochores to microtubules and in cytokinesis. We report here that Aurora B contains a conserved SUMO modification motif within its kinase domain. Aurora B can bind SUMO peptides in vitro when bound to the IN-box domain of its CPC partner INCENP. Mutation of Lys207 to arginine (Aurora BK207R) impairs the formation of conjugates of Aurora B and SUMO in vivo. Expression of the SUMO-null form of Aurora B results in abnormal chromosome segregation and cytokinesis failure and it is not able to rescue mitotic defects in Aurora-B-knockout cells. These defects are accompanied by increased levels of the CPC on chromosome arms and defective centromeric function, as detected by decreased phosphorylation of the Aurora-B substrate CENP-A. The Aurora-BK207R mutant does not display reduced kinase activity, suggesting that functional defects are probably a consequence of the altered localization, rather than decreased intrinsic kinase activity. These data suggest that SUMOylation of Aurora B modulates its function, possibly by mediating the extraction of CPC complexes from chromosome arms during prometaphase. Key words: Aurora kinases, Cell cycle, Chromosome segregation, Cancer target, SUMO modifications Introduction the others, disrupts mitotic progression and might destabilize one Aurora B (serine/threonine-protein kinase 12) is the enzymatic or more subunits (Jeyaprakash et al., 2007; Ruchaud et al., 2007). Journal of Cell Science core of a multiprotein complex, the chromosomal passenger In addition, several post-translational modifications are known to complex (CPC), which comprises other three non-enzymatic be required for proper activity and control of the dynamic behavior subunits, INCENP, Survivin and Borealin (Carmena and Earnshaw, of the CPC. Activation of Aurora B is triggered by 2003; Ruchaud et al., 2007). The CPC is an important upstream autophosphorylation of the T-loop residue after association with its regulator of centromere-kinetochore function, and is responsible substrate, INCENP. Full activation involves a positive-feedback for the recruitment to the kinetochore and centromere of a number loop after Aurora-B phosphorylation of INCENP in the conserved of proteins, including inner centromere-kinetochore proteins (Sgo1, IN-box region, possibly as a result of structural rearrangements Sgo2, MCAK), regulators of the microtubule-kinetochore (Bishop and Schumacher, 2002; Honda et al., 2003). interaction (such as Hec1 and Plk1, among others) and proteins CPC function is also modulated by ubiquitin and ubiquitin- involved in the spindle-assembly checkpoint (SAC; such as Mad2, related modifiers. Aurora B is targeted by a Cul3-containing SCF BubR1 and Mps1) (Kelly and Funabiki, 2009; Ruchaud et al., ubiquitin ligase during early mitosis (Sumara et al., 2007). 2007). Some kinetochore components, including Hec1, Dam1, Interestingly, this modification is necessary to remove a fraction MCAK and CENP-A, are Aurora-B substrates, suggesting a crucial of Aurora B from mitotic chromosomes, allowing its accumulation role for the CPC in the destabilization of aberrant microtubule-to- on the central spindle during anaphase. In the absence of this kinetochore attachments and in the SAC-dependent delay of mitotic SCF-Cul3 ubiquitin ligase, Aurora B spreads along chromosome progression until these defects are corrected. Recent data suggests arms and fails to dissociate from them during anaphase. Aurora that substrate phosphorylation depends on the distance of the B also requires APC/C-Cdh1 activity to efficiently translocate to substrate from Aurora B at the inner centromere, and artificial the spindle mid-zone in anaphase. In APC/C-Cdh1-depleted cells recruitment of the CPC to the kinetochore prevents the stabilization Aurora B and the CPC prematurely accumulate in the equatorial of improper attachments and activates the SAC to delay the cortex, resulting in a weak anaphase spindle (Floyd et al., 2008). metaphase-to-anaphase transition (Kelly and Funabiki, 2009; Liu Finally, after completion of cytokinesis, the remaining pool of et al., 2009). During cytokinesis, Aurora B is localized to the mid- Aurora B is targeted for degradation by APC/C-Cdh1 (Floyd et body where its local inactivation is crucial for completion of al., 2008; Garcia-Higuera et al., 2008). These post-translational abscission (Guse et al., 2005; Steigemann et al., 2009). modifications also affect other CPC components. For instance, Activity of Aurora B is regulated through several mechanisms, Survivin is ubiquitylated during mitosis and its deubiquitylation including controlled interactions with INCENP, Survivin and is required for Survivin dynamics at centromeres (Vong et al., Borealin. Knockdown of any member of the complex delocalizes 2005). 2824 Journal of Cell Science 123 (16) Post-translational modifications by the covalent attachment of small ubiquitin-related modifiers (SUMOs) are important in several cellular processes, including the cell-division cycle (Geiss- Friedlander and Melchior, 2007; Hay, 2005; Ulrich, 2008). In vertebrates, at least three SUMO forms (SUMO1, SUMO2 and SUMO3) are covalently attached to a lysine residue in the target protein in three enzymatic steps analogous to the ubiquitylation cascade. SUMO conjugation requires a SUMO-activating E1 enzyme (SAE1 or SAE2), the SUMO-conjugating E2 enzyme UBC9 and, in some cases, additional E3 SUMO ligases (Hay, 2005). SUMO modification is reversible by the action of SUMO- specific isopeptidases that belong to the family of ubiquitin-like proteases (ULPs), also known as sentrin-specific proteases (SENPs) (Hay, 2007). Recent work has revealed the importance of SUMOylation for mitotic progression (Dasso, 2008; Watts, 2007) and has suggested a crucial role of SUMO modifications in kinetochore and centromere function (Dawlaty et al., 2008; Di Bacco et al., 2006; Mukhopadhyay et al., 2010; Zhang et al., 2008), including direct SUMOylation of the CPC component Borealin (Klein et al., 2009). In this manuscript, we provide evidence for SUMOylation of Aurora B at Lys207. Mutation of this residue results in abnormal mitotic progression and the generation of multinucleated cells. In those mutant cells, Aurora B and INCENP display an abnormal localization at the chromosome arms during prometaphase and metaphase and defective CENP-A phosphorylation, indicating a Fig. 1. A SUMOylation motif in Aurora B. (A)Multiple sequence alignment role for Aurora-B SUMOylation in the proper localization and of Aurora B proteins from different species using Clustal software. Mm, Mus activity of the CPC during chromosome alignment. musculus; Rn, Rattus norvegicus; Hs, Homo sapiens; Xl, Xenopus laevis; Dm, Drosophila melanogaster; Ce, Caenorhabditis elegans; Sc, single Aurora family member (Ipl1) from Saccharomyces cerevisiae. The SUMO motif Results (green box) is highly conserved in all these Aurora-B proteins, as well as in A conserved SUMOylation motif in Aurora-B proteins Aurora A and Aurora C, but it is not present in Polo-like kinase 4 (Plk4), a Aurora B contains a consensus motif for SUMO modification (- close mitotic relative of these mitotic kinases. The kinase domain is shown in Lys-x-Glu, in which is a hydrophobic residue and x, any residue) dark blue, whereas the degradation motifs (KEN, A- and D-boxes) are within the kinase domain (Fig. 1A). This motif is readily identified represented as red boxes. Note that the SUMO motif is located one residue Journal of Cell Science by using different protein- domain-recognition algorithms (see the downstream of the aspartate (D205) that is crucial for ATP binding. Residue Materials and Methods). The SUMO motif is conserved among numbers correspond to the mouse Aurora-B protein. (B)In vivo SUMOylation Aurora-B orthologues from yeast to human, and it is also present of Aurora B at K207. HEK293 asynchronous cells were transiently transfected K207R in the other mammalian members of the Aurora family, but not in with vectors expressing V5-Aurora-B WT, Aurora B , HA-SUMO1, other cell cycle kinases, including Polo-like kinases (Fig. 1A). -SUMO2 or -SUMO3 and the E2 SUMO ligase UBC9, as indicated. The empty vector pDEST-V5 was used as a negative control. V5-Aurora-B To test the possible SUMOylation of this domain, we mutated proteins were immunoprecipitated (IP) 48 hours after transfection using anti- the lysine (K207) predicted to accept the SUMO peptide into a V5 antibodies and immunoblotted (IB) with antibodies against the HA and V5 K207R charge-conservative arginine residue. The Aurora-B mutation tags. Aurora-B-SUMO conjugates are found after detection of the HA